Radioactivity And Particles Flashcards
Define Isotopes?
Same number of protons but different number of neutrons
What is Radioactive decay
Nuclei of unstable isotope break down randomly
Where does background nuclear radiation come from?
- Substances on Earth - air, food, building materials, soil, rocks
- Cosmic Rays
- Human activity - fallout of nuclear explosion or waste
How does Nuclear Radiation cause Ionisation?
- By bashing into atoms + knocking electrons off them
* Atoms (no charge) turning into ions (charged) = ionisation
How can something be Less Ionising?
Further radiation penetrates before hitting an atom + getting stopped, the less damage it will do along the way - less ionising
How can Ionising Radiation be detected?
- Geiger Muller (GM) detector
* Photographic film
What are the different types of Ionising Radiation?
- Alpha Particles
- Beta Particles
- Gamma Rays
What are Alpha Particles?
- Helium nuclei
- 2 protons + neutrons
- Don’t penetrate far
- Big, heavy, slow moving
- Strongly ionising - bash into a lot of atoms+ knock off electrons before slow down = ions
- Deflected (direction changes) by electric + magnetic fields because positively charged
What are Beta Particles?
- Electrons
- Fast moving, small
- Penetrate moderately before colliding + moderately ionising
- Negatively charged
- Deflected by electric + magnetic fields
What are Gamma Rays?
- Short wavelength EM waves
- Penetrate far into materials
- Weakly ionising - pass through rather then collide with atoms
- No charge - not deflected by electric or magnetic fields
When do Gamma Emissions happen?
After beta of alpha decay
What is Alpha Particles penetrated by?
Blocked by paper, skin, few cm of air
What is Beta Particles penetrated by?
Blocked by thin metal (aluminium )
What is Gamma Rays penetrated by?
Blocked by thick lead or very thick concrete
How can you Investigate the Penetration of Radiation?
•GM
What does the GM detector do?
Gives a count rate - number of radioactive particles reaching it per second
How can you Investigate the Penetration of Radiation?
- Attach radioactive source to material+GM detector+counter
- Remove source to measure background count over time period
- Divide count by time period to get background count per sec
- Repeat + find mean
- Replace source + measure count rate with no material + repeat + find mean
- Insert different material,record count,repeat
- If count rate remains same when material inserted - Radiation can penetrate the material
How do you Prevent Radioactive Sources from being Dangerous?
- Keep then in lead-lined box
- Pick them up using long tongs
- Don’t point them at anyone, keep a safe distance from them
What is the Alpha emission?
- Mass number decreases by 4
* Atomic number decreases by 2
What is the Beta emission?
- Mass number stays the same
* Atomic number increases by 1
What is the Gamma emission?
Mass and atomic number stays the same
What is the Neutron emission?
- Mass number decreases by 1
* Atomic number stays the same
